The present invention relates to a semiconductor design technology, and more particularly, to a technology for monitoring the electrical resistance of an element such as a fuse whose resistance changes due to the electrical stress among internal circuits included in a semiconductor device.
As the highly-integrated technology of a semiconductor memory device is developed, the number of memory cells and signal lines included in a single semiconductor memory device has been rapidly increased, and line width is narrowed and the size of a memory cell is getting smaller since the memory cells and signal lines are integrated in a limited area. Due to the above-mentioned reasons, the possibility of having a defective memory cell in the semiconductor memory device is increased; however, although there may be a defective memory cell, the semiconductor memory device having an expected capacity can still be manufactured with a high production yield because there is a redundancy circuit included in the semiconductor memory device for remedying the defective memory cell. The redundancy circuit includes a fuse or the like for programming a repair address which corresponds to a redundancy memory cell and a defective memory cell. Generally, if a wafer process is completed, various testes are performed and repairable defective memory cells among detected defective memory cells are remedied by replacing those cells with redundancy memory cells. That is, an internal circuit performs a programming for changing an address which corresponds to a defective memory cell with an address which corresponds to a redundancy memory cell. Accordingly, if the address which corresponds to the defective memory cell is inputted, the defective memory cell is replaced with the redundancy memory cell so that a normal operation is performed. For programming address information which corresponds to the defective memory cell, a fuse programming method is mostly used. In case of applying a laser beam or an electrical stress to the fuse, the electrical characteristic of the fuse is changed, and thus the electrical resistance is changed. By using this electrical connection state of the fuse, an address is programmed.
A laser blowing-type fuse which disconnects the connection state of the fuse by using the laser beam is generally called a physical fuse type and is performed in a wafer state. Herein, the wafer state is a step prior to the step in which the semiconductor memory device is manufactured to a package. In the package state, an electrical method is used instead of the physical method which uses the laser. A fuse which is programmable in the package state is generally called an electrical fuse, which means that a programming is possible by changing the electrical connection of the fuse by applying the electrical stress. Such an electrical fuse can be classified into one of two types: an anti-type fuse which changes an open state to a short state, or an blowing-type fuse which changes the short state to the open state. The utility of the above-mentioned electrical fuse is very high in the package state since the electrical fuse is used for programming after packaging.
Since the programming of the electrical fuse is performed in the package state, it is difficult to visually detect the characteristics change and electrical connection of the fuse while the programming is performed, and it is possible to detect the state of the fuse by testing an operation of the semiconductor device after the programming. Furthermore, since the electrical stress applied to the fuse while the programming is in progress is higher than an electrical applying condition for a general operation, a deterioration of the device characteristics may occur. Therefore, it is important to find an optimum condition for stably programming the fuse in order to effectively use the electrical fuse; however, it is very difficult to find the optimized programming condition in batches by reflecting different process conditions of semiconductor devices. Therefore, when a device such as the fuse which stores information according to the electrical connection state, it is required to correctly find an optimum applying condition for changing its resistance to a predetermined electrical resistance.